This application claims the priority of 198 38 755.5-13, filed Aug. 26, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a fuel injection nozzle injecting onto the combustion space of an internal combustion engine. More particularly, it relates to a nozzle which is to is be arranged in a nozzle receptacle located on the same side as the internal combustion engine and open towards the combustion space and has a nozzle body and a nozzle neck stepped relative to the nozzle body. An injection orifice is arranged at the neck end located on the combustion-space side and which is assigned, in the neck region, a shielding sleeve which is located radially on the outside with a clearance relative to the surrounding nozzle receptacle and, starting from one of its ends, bears radially on the inside on the neck without any play via one axial part region and, via another part region, delimits relative to the neck an annular gap and which is provided, at its end facing the nozzle body, with an annular collar which is capable of being clamped in the region of the neck start between the nozzle body and nozzle receptacle.
Fuel injection nozzles are known as seen in German Patent Specification 873,011, particularly FIGS. 2 and 3. If they have a conventional design and conventional functioning, they consist of a nozzle body and a nozzle neck which is stepped in diameter relative to the nozzle body and which has, at the end located on the combustion-space side, at least one injection orifice which is controlled via the nozzle needle and is assigned a shielding sleeve. The shielding sleeve is arranged radially on the outside, with a clearance relative to the surrounding nozzle receptacle, and the corresponding annular gap, starting from the combustion space, extends as far as an annular collar which is assigned to the neck starting region and which is capable of being clamped between bearing surfaces of the nozzle body and of the nozzle receptacle. Starting from the combustion space, an annular gap is provided between the nozzle neck and shielding sleeve. The annular gap does not, however, extend into the upper end region of the nozzle neck, because in this region the shielding sleeve bears with a press fit on the neck and is connected positively to the nozzle neck by, for example, being rolled on.
The result of this design and mounting of the shielding sleeve is that the latter overlaps the nozzle neck virtually completely and, because of the annular gap on the combustion-space side between the shielding sleeve and nozzle neck, is capable of reducing the incidence of heat on the nozzle neck. Also, because of the press-fit connection made in the neck starting region between the nozzle neck and shielding sleeve, this design ensures relatively good heat transmission between the nozzle neck and shielding sleeve, thus resulting in a good transport of heat to the nozzle receptacle.
At the same time, however, by virtue of the above known design the nozzle is loaded and, if appropriate, braced, during production, in the area of the critical region of transition of the nozzle body to the nozzle neck. This is critical on account of the extremely narrow fitting conditions for the nozzle needle and the sliding guidance of the latter which should be as free of play as possible. Furthermore, a design of this kind means that production is relatively complicated and that there are difficulties with regard to the exchangeability of the shielding sleeve in the event of a repair.